Hey edsel, you might be right about that.
I decided at the beginning to take the hard road and farm every soul regardless.
But, comparing the economics in hindsight . . .
I didn't keep careful track of ironite returned via drops, but I estimate that the net cost per mega was 130 ironite. So, 56 megas would have cost 7,280 ironite. So about 500 more ironite than buying the 75 souls directly.
But, that extra 500 ironite got me over 5,000 Floor X runs worth of leveling and evo materials, plus over 7,500 Lilith frags (15 Liliths). [Those 7,500 Lilith frags are drops, in addition to the frags granted from the sinful souls.]
In either case, she was expensive.